Plunger seal



Feb. 1, 1955 F. A. KOESTER 2,701,172

PLUNGER SEAL' Filed May .26, 1950 J IN V EN TOR.

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United States Patent PLUNGER SEAL Frederick A. Koester, Los Angeles,Calif.

Application May 26, 1950, Serial No. 164,385

2 Claims. (Cl. 309-4) My invention relates to plunger seals and mypresent application is a continuation-in-part of my previously filedapplication, Serial No. 55,047, filed October 18, 1948, entitled PlungerSeal and now abandoned.

Included in the objects of my invention are:

First, to provide a plunger seal which is particularly suitable formanufacturing in small sizes and which has a low friction factor,thereby providing a plunger seal which is particularly suitable for usein air gauges such as tire pressure gauges, air line hand valves, andtire inflation valves.

Second, to provide a plunger seal which employs a cup leather backed bya molded expansion member formed of rubber or so-called syntheticrubber, the expansion member being so mounted as to avoid cold flow ordisplacement even under conditions of long and adverse use.

With the above and other objects in view as may appear hereinafter,reference is made to the accompanying drawings, in which:

Figure 1 is an enlarged sectional view of a plunger incorporating myplunger seal.

Figure 2 is an enlarged end view of the assembled plunger seal, with aportion of the retaining cap broken away.

Figure 3 is an exploded view, partially in section, showing the variousindividual elements of my invention.

My plunger seal includes a plunger stem or mandrel 1 having an integralhead 2. The stem 1 receives an outer cup 3 preferably formed of leatherand molded to provide a perforated base 4, diverging side walls 5 and askived or beveled wiping edge 6. The outer cup 3 journals freely on themandrel 1.

The outer cup 3 receives an inner cup 7 molded of rubber or rubberlikeplastic material. It likewise includes a perforated base 8 and divergingside walls 9. The inner cup likewise journals on the mandrel 1, but

2,701,172 Patented Feb. 1, 1955 preferably fits thereon more snugly thanthe outer cup 3. Furthermore, the diverging side walls diverge atsomewhat greater angle than the side walls 5, so that the rim portiononly of the side walls 9 bear against the side walls 5 of the outer cupadjacent the skived edge 6.

The mandrel 1 receives a cap 10 having a socket 11 adapted to bepressfitted on the mandrel. To facilitate assembly, the extremity of themandrel or the opening of the bore 11 may be slightly tapered. The boreor socket 11 does not extend entirely through the cap 10, however, asmaller bleeder hole 12 may be provided for the escape of air duringassembly. The depth of the socket or bore 11 is such, that when theparts of the plunger seal are assembled, as shown in Figure 1, the capis limited in its movement over the mandrel so as to avoid anyappreciable axial compression of the outer and inner cups. This isimportant for the reason that the plastic materials most suited for useas the inner cup have a tendency to cold flow under pressure. Byavoiding conditions of pressure in the inner cup, there is little or nocold flow even under adverse conditions.

Having fully described my invention, it is to be understood that I do-not wish to be limited to the details herein set forth, but myinvention is of the full scope of the appended claims.

I claim:

1. A plunger seal involving: a stem having a head; an outer sealing cupand an inner backing cup rotatably mounted on said stern; a collarmember adapted to be press fitted on said stem and having a stop wherebysaid collar may retain said cups on said stem without axial pressurethereon.

2. A plunger seal involving: a stem having a head; an outer sealing cupand an inner backing cup rotatably mounted on said stem; a collar memberadapted to be press fitted on said stem and having a stop whereby saidcollar may retain said cups on said stem without axial pressure thereon;said backing cup being molded to fit freely in said outer cup withradial bearing pressure only at the rims of said cups.

References Cited in the file of this patent UNITED STATES PATENTS 45,989Fuller Jan. 24, 1865 56,757 Jewell July 31, 1866 181,226 Vander EmdeAug. 15, 1876 772,457 Cramer Oct. 18, 1904 1,543,505 Middleton et al.June 23, 1925 2,246,685 Johansen June 24, 1941 2,271,746 Schmalz Feb. 3,1942 2,598,975 Coulter June 3, 1952

